Epoxy resin non official thickeners

[andrewbartlett]

Im constructing a plywood boat using epoxy resin for the first time. To make the resin suitably thick e.g. peanut butter type thickness, can handy every day supplies be used such as sawdust or anything else easily to hand e.g flour??

 

[KellysEye]

Why would you want to do that?

 

[ReefMagnet]

Well you should use the proper stuff like colloidal silica which isn't that dear, but I once used fine sawdust which seemed to work. Don't think I'd use it for anything other than fairing but.

 

[oldbilbo]

Im constructing a plywood boat using epoxy resin for the first time. To make the resin suitably thick e.g. peanut butter type thickness, can handy every day supplies be used such as sawdust or anything else easily to hand e.g flour??

Your answer lies in the seminal book 'Gougeon Brothers On Boat Construction' and various leaflets - some online - from West Products/Wessex Resins, and the simple answer is 'Yes'. Some materials are more effective than others, and certainly wood dust and flour has been used. However, finely shredded rags and silica powder are available quite cheaply from resin suppliers in most towns, for this purpose, and you might well benefit from defining your task(s) and choosing the filler material appropriately.

There's merit in making a couple of test-pieces, curing them, and then loading them to destruction. If the wood/ply breaks before the bond-joint, you've got it about right.

 

[Rigger Mortice]

I've used talcum powder successfully.

 

[mezereon]

I save my sawdust for exactly this purpose and have used it many times without any problems. For a strong joint I would always try to have close fitting joints and use the unadulterated epoxy, but for fairing, filling and filleting, why not?
NB the size of the sawdust particles is significant. Finer is better.

 

[30boat]

Another one for talcum powder.I buy it by weight and it's very cheap.It makes a very good filler/glue.Sawdust is also perfectly good,finer is better.

 

[John the kiwi]

Maybe i was doing it wrong, but when i built my stitch and tape dinghy i thought i would use sawdust for filling the seam fillets.
Test pieces were dreadful. Difficult to apply and rough when i did.
I bought a bag of micro balloons. Not overly expensive and they go a long way. Smooth to mix and apply and easy enough to sand.
Finished the dinghy and still use the same bag for odd filling jobs. Dont think i will run out soon.
I still don't know what a micro balloon is though.

 

[ningcompoop]

If you're doing a complete build (as opposed to a little repair work) I would imagine the epoxy you're using is one on the more expensive components of the build, I'd just be concerned that taking shortcuts with the filler might be counter-productive - inappropriate or contaminated filler could lead to problems with the epoxy cure and strength, improperly cured epoxy is a real pain to remove. If you've got access to a good supply of clean, dry, unadulterated sawdust or fine fibres then try doing some test mixes and see how they go. As Bilbo suggested above, West have produced numerous guides (Your starter for ten: http://www.cfsnet.co.uk/acatalog/Epoxy_User_Manual.html), most of which you can download for free from the web; have a browse, if you haven't already. Most of the info on techniques is applicable to any manufacturer's resins.

(But not the resin/hardener ratios - always follow manufacturer's instructions!)

 

[Rigger Mortice]

I still don't know what a micro balloon is though.

A small hollow glass bead.

 

[Tranona]

The type of filler you use will depend on how you are using epoxy. The two main purposes of fillers are to bulk out the volume and make the mixture easier to handle. The more you bulk it out the lower the strength. The fillers sold commercially have been developed with different applications in mind and you can find information on them on either the Wessex Resins website or in the Gougeon Brothers book already suggested. The most commonly used fillers are silica for strong bonds (but very hard to sand), wood fibres for bulking out for filleting, low density and high density microballoon based fillers for filleting and fairing and various glass based additives and reinforcement materials. Other materials such as talcum powder and sawdust can be used where you are not too bothered about strength - not that they are necessarily inferior, but the strength of the finished product is not so predictable.

 

[oldbilbo]

On a slight tangent - or maybe a parallel track -I had need today to secure a patch to a section of uPVC 110mm waste-pipe. I thought I knew, but phoned the Tech Help people at OSMA-Wavin, who advised that the Solvent Cement they sell which is intended for solvent-bonding of fittings is good, but thin and runny. It is optimum where the two surfaces to be bonded are a fairly tight push-fit.

Where a patch is needed, they recommend a Thickened Solvent Cement, to ensure that any small gaps are filled. Despite reading from the COSH leaflet, we/they were unable to determine what material is used as a filler, and none of the builders/plumbers merchants around here had any in stock ( quelle surprise! ) so I filed some dust off the end of a spare piece of plasterboard and used that to thicken the gloop.

I'll let you know....

 

[BruceDanforth]

Half boat, half bagel...

Im constructing a plywood boat using epoxy resin for the first time. To make the resin suitably thick e.g. peanut butter type thickness, can handy every day supplies be used such as sawdust or anything else easily to hand e.g flour??

 

[Lakesailor]

Im constructing a plywood boat using epoxy resin for the first time. To make the resin suitably thick e.g. peanut butter type thickness, can handy every day supplies be used such as sawdust or anything else easily to hand e.g flour??

If you use sawdust (fine) of the same wood that you are using it is colour-keyed which is handy. It is also far easier to fair than any micro balloons.
You can buy wood dust, http://www.fyneboatkits.co.uk/other/epoxy/epoxy-filler/ but far more economical to go to a joiner's workshop and get a bucket of their dust which they will be collecting in the course of their work.

 

[TQA]

One thing to very aware of is that different fillers sand very differently.

EG Colloidal silica is hard to sand and Micro balloons fairly easy.

If using sawdust make sure it is bone dry as moisture inhibits curing and you finish up with stuff that behaves like chewing gum.

Another is that not all fillers are suitable for use below the waterline. I only use colloidal silica below the waterline.

 

[30boat]

If you use sawdust (fine) of the same wood that you are using it is colour-keyed which is handy. It is also far easier to fair than any micro balloons.
You can buy wood dust, http://www.fyneboatkits.co.uk/other/epoxy/epoxy-filler/ but far more economical to go to a joiner's workshop and get a bucket of their dust which they will be collecting in the course of their work.

I read on a book that a good source of wood flour is the bread industry.Apparently it's used to increase the bread's fiber content.But that was in an American book from 20 years ago.

 

[Ardenfour]

Done loads of work with epoxy thickened with custard powder, all I had handy - the strength surely is in the epoxy, not the filler, so providing there's no chemical reaction, anything will do.

 

[lw395]

I think a point that's not been made is the density and epoxy content of the mix.
Microballoons or glass bubbles may use a lot less epoxy and hence be lighter and cheaper for a given size of fillet, you have to optimise that against the strength.
sawdust will soak up a lot of epoxy and be quite strong but dense.
A bigger fillet of less dense goo may be stronger as a whole.

 

[30boat]

A bigger fillet of less dense goo may be stronger as a whole.

I agree.The structure of bone comes to mind.

 

[fishermantwo]

It all depends on what your using this filler for. I use micro balloons a lot. Sometimes by itself but if I am after strength I use the micro balloons to smooth out other fillers. Sawdust, brass and SS filings, sand. Crushed granite is one of the strongest fillers. Used with out micro balloons its hard to get a paste constituency. Caution is required if your sanding or grinding resin filled with sand, silica dust is not good for you. Brass filled resin is ideal for items turned up on a lathe. I'm sure there is a helpful list of suitable fillers somewhere but I don't think resellers are going to broadcast them to compete against their expensive products.